Create whitelist for all labels not used for controller or service selection to improve query performance and memory usage.

[AjayTripathy]

Is your feature request related to a problem? Please describe.
See #2637 . Labels can be a considerable portion of opencost and the backing prometheus memory footprint.

Describe the solution you'd like

• We can know a priori via the kubernetes API which labels are important for selection into a controller/service by looking up the selector lables, and automatically emit those
• The end user can add meaningful other labels on a whitelist.

Estimated impact: I'm guessing this would reduce the size of the stored data in prometheus by 30% or so, so likely a 30% speedup in query time and query memory usage.

Describe alternatives you've considered
There may be other improvements about what to store in memory from the k8s api; but that work won't impact prometheus memory.

[r2k1]

I think alternatively a new metric (or multiple metrics) exposing relationship between pod/controller, pod/service can be added.
It will further reduce the memory footprint and may simplify aggregation logic.

[AjayTripathy]

It's been awhile since I've been in that code, but keeping a subset of labels feels simpler than creating new ones and about the same order of magnitude, plus a whitelist will allow other labels important to the user to still be kept?

[r2k1]

Labels serve two main purposes:

• They group pods under controllers.
• They help allocate costs based on labels.

A solution for one may not be ideal for another.

I can't dictate the labels users choose for their deployments or services, leading to a vast variety of labels. Each deployment might use a unique set of these labels.

Exporting varying labels for different pods could lead to inaccuracies when such labels are used for aggregation.

[r2k1]

Overall, this solution may fix my issue, but need to be careful allowing users to use all labels for aggregation purposes.

[AjayTripathy]

#2719 takes a quick pass at this.